I've got one of these, and I love it!
It's made my Tech Air, and comes with a little card saying who checked it. It comes with some good sized pockets both front and rear, and an MP3 player pocket that's big enough for an MP3 player (headphones do fit through the little gap, so less chance of losing it!) and also perhaps a wallet or a train/bus pass, so you never have to worry a about losing it.
Inside the bag, there's a dedicated laptop pocket, which is easily big enough for a 15.4" screen laptop (my Macbook fits in there nicely) It's nicely padded both front and back of the pocket, and has a little velcro part to stop the laptop shifting too much (you can stick it down so it's the same height as the top of the laptop, so keeping it in place securely)
There's also a front compartment, which can take either an A4 pad or thin folder (probably a portfolio not a ring binder) and it has some smaller pockets on the front of the compartment, which can be used for keys/pens/dictaphone/anything you need to put in there.
In between the laptop and front compartment, there's also enough space between to put a lunch box and flask, or to store any other books/accessories which might be needed. I manage to fit in my charger, a lunch box, a 0.5 flask and another 2-3 books in the front, dependant on height and width.
There's also another interesting feature; the i-Trak service. There's a little label stitched on with a number attached, and another label to attach to your laptop. If either the bag or your laptop go missing, let i-Trak know and they can trace them anywhere in the world. The bag comes with a free year's subscription to i-Trak, and I'm not sure how much it is to renew, not having registered mine yet (naughty and slapped hands!)
All in all, even considering the price, it's an extremely useful and durable bag, which I now use every day for uni, even when not taking my Macbook. It's waterproof, the pockets are easy to get to, open and close and the zips are secure. It's also quite robust, so isn't going to fall apart after a couple of months. This is perfect as either a commuter bag, or to use if travelling on business, as you could easily fit a laptop and overnight stuff in the bag (but your shirt may need to go in the book compartment to stop it getting crumpled.